At present, syringes are delivered with a protector enabling them to be conserved under sterile conditions prior to use, and also enabling them to be covered after use so as to protect anyone handling the used syringe from any contamination that could result from unintentional pricks.
These dispositions are not capable of eliminating all danger of contamination after use since the user needs to put the cap back on the needle, and it is during this operation that the risk of pricking oneself is high. Furthermore, syringes re-capped in this way can still be reused, and that is very much to be avoided. That is why, in some cases, the needle in a protector is fixed to the syringe and, after use, is removed from the syringe and is broken so as to prevent reuse. Nevertheless, there remains a risk of the user being pricked during this final manipulation.
It is also recalled that certain present-day syringes include a cylindrical case having one end closed either by a partition in which the injection needle is implanted, or else by an endpiece that carries an add-on needle, and is open at its opposite end so as to receive a flask of substance to be injected, with the perforatable wall thereof being directed towards the portion of the needle that projects into the case, the case then being closed again by a plug which includes a piston for acting on a moving wall of the flask opposite from its perforatable wall.
The invention provides an improvement both over conventional syringes and over syringes of the above composite type with respect to ensuring protection of the needle prior to use, and to putting the needle out of reach after use, making it impossible to reuse the needle.
It is known that the needle can be isolated by means of a tubular sheath that slides on the body of the syringe, which sheath is placed around the needle from a position in which it uncovers the needle. Mention may be made, for example, of syringes as described in the documents U.S. Pat. No. 4,911,693 and EP-A-0 250 104.
The device described in the first document is adapted to syringes having long needles, since the device is carried by the needle only. It is therefore unsuitable for cartridge syringes of the kind used in dentistry, in particular.
The device described in the second document does not provide a genuine guarantee of preventing syringe reuse, since the locking members are accessible to anyone seeking to manipulate them.